When the U.S. beat Mexico in prime time at Azteca Stadium in August for the first time, as many as 9.4 million viewers watched all or part of the game on Univision, more than any other network that evening in the coveted 18-34 demographic.

In contrast, just fewer than 800,000 viewers watched the historic game on ESPN2 (Univision averaged

more than

4.5 million).

Even given that many English-language soccer fans favor Spanish-language coverage over the quantity and quality on ESPN, the respective viewership reflects a stunningly huge disparity in the interest in the game between the Mexican-American and Anglo cultures.

What’s more, in Mexico and U.S. Spanish-language media the shocking result was front-page news. Many English-language U.S. newspapers didn’t even have the game story on the front cover of the sports section and instead buried it inside.

The reaction from the two soccer cultures tells everything you need to know about the importance of what is one of the best rivalries in world soccer in the respective nations.

“Most American fans didn’t know we hadn’t won in 75 years (of trying), whereas most Mexican fans knew they had never lost to the U.S. on home soil,” said Echo Park resident Pablo Miralles, one of the filmmakers behind the independent documentary “Gringos at the Gate.”

The film, four years in the making, traces the history and increasing significance of the rivalry on and off the pitch. It has its West coast premier at 6 p.m. Sunday at the Downtown Independent Theater in Los Angeles. For tickets, to pre-order the DVD scheduled for release later this year, or for more information, visit www.gringosatthegate.com.

It is in a sense the definitive Southern California soccer movie. You cannot understand soccer in Southern California without some appreciation of the U.S.-Mexico rivalry.

The filmmakers effectively mine rich, local soccer resources to tell the story. They interview Spanish-speaking former Galaxy coach Steve Sampson, L.A. native and former Galaxy striker Herculez Gomez, now playing in Mexico, and former local players Eric Wynalda, Cobi Jones, Rick Davis and Paul Caliguri.

Miralles, born to an Argentine father and Dutch mother, grew up in Altadena playing soccer in a league his father helped found and watching the old L.A. Aztecs play in the NASL.

He made the movie in partnership with fellow UCLA film school grads Michael Whalen and Mexico City native Robert Donati after watching the U.S knock out Mexico in the 2002 World Cup. It was the first time the nations had met in a World Cup, and the result still stings El Tri fans a decade later.

The result crystallized for Miralles how he could tell the story of soccer’s growth and evolution in the U.S. and what that would mean for Mexico, for decades the sport’s dominant power in the region.

“This is how I can explain to people the United States has come of age at some level,” he said. “It seemed to me to be a great source to show the development of U.S. soccer in my lifetime.”

The main theme of the movie is readily apparent. Most U.S. sports fans care little for a rivalry that goes to the very heart of Mexico’s national identity.

But the filmmakers try to delve deeper and explain what the growing U.S. prowess in soccer means for the development and future of the sport in both nations.

For instance, it didn’t escape the attention of Mexicans that a half dozen of the players on the victorious U.S. team played south of the border. Indeed, Miralles believes that’s helping spur the development of the youth system in Mexico, most recently expressed at the Olympics when a team of largely Under-23 players took the gold medal.

“In my opinion they are doing well because of the United States, because they are feeling threatened by this neighbor they used to beat easily,” he said. “It’s beneficial to both sides that this rivalry exists.”

And it is changing as the years pass.

Some Mexican-Americans are opting to cheer for the U.S. rather than their parents’ homeland.

The Mexican league is an increasingly viable option for Mexican-Americans to play in professionally rather than wait to be spotted in the white-dominated youth soccer system here.

And what happens, Miralles wonders, if Mexico – or imagine – the U.S. wins a World Cup or comes close in his lifetime?

“By no means are we at the end of this thing,” Miralles said. “It has evolved in the four years we started making this movie.”

Veteran journalist Nick Green is the beat reporter for the cities of Torrance, Carson and Lomita and also covers the South Bay's rapidly growing craft beer industry for the Daily Breeze. He has worked for newspapers on the West Coast since graduating in 1987 from the University of Washington and lives in Old Torrance with his wife and two cats. Follow him on Twitter @NickGreen007 and @BeerGogglesLA.